In a manufacturing process of a semiconductor device, various films having different physical properties are formed on a silicon substrate and these films are subjected to various processes, thus forming fine metal interconnects. For example, in a damascene interconnect forming process, interconnect trenches are formed in a film and are then filled with metal, such as Cu. Thereafter, an excessive metal is removed by chemical mechanical polishing (CMP), so that metal interconnects are formed. A CMP apparatus (polishing apparatus) for polishing a substrate typically includes a substrate cleaning apparatus for cleaning a polished substrate. Cleaning of the substrate is performed by rubbing a scrub-cleaning tool, such as a roll sponge, against the substrate while rotating the substrate horizontally.
As the scrub-cleaning tool cleans substrate(s), abrasive grains used in CMP and polishing debris (hereinafter, these will collectively be referred to as processing debris) are accumulated in the scrub-cleaning tool. Therefore, in order to remove these processing debris from the scrub-cleaning tool, cleaning of the scrub-cleaning tool is periodically performed. Cleaning of the scrub-cleaning tool is performed by a self-cleaning device disposed adjacent to the substrate cleaning apparatus. More specifically, the scrub-cleaning tool is transported to the self-cleaning device after cleaning the substrate, and is then cleaned by a brush or a plate that contacts the scrub-cleaning tool, while the scrub-cleaning tool is rotated (see Japanese laid-open patent publication No. 2005-12238).
However, this conventional contact-type self-cleaning device has a problem that the processing debris that has been once removed is transferred from the brush or plate to the scrub-cleaning tool, thus causing back contamination of the scrub-cleaning tool and the substrate.